This invention relates to smoking articles in which tobacco flavor media are heated but not burned to release tobacco flavors. More particularly, this invention relates to electrical smoking articles.
An electrical smoking generating article is described in commonly-assigned U.S. patent application Ser. No. 07/444,746, filed Dec. 1, 1989, now U.S. Pat. No. 5,060,671, which was copending with parent application Ser. No. 07/666,926, filed Mar. 11, 1991, and which is hereby incorporated by reference in its entirety. That application describes an electrical smoking article which is provided with a disposable set of electrical heating elements on each of which is deposited an individual charge of tobacco flavor medium containing, for example, tobacco or tobacco-derived material. The disposable heater/flavor unit is mated to a more or less permanent unit containing a source of electrical energy such as a battery or capacitor, as well as control circuitry to actuate the heating elements in response to a puff by a smoker on the article or the depression of a manual switch. The circuitry is designed so that at least one but less than all of the heating elements are actuated for any one puff, so that a pre-determined number of puffs, each containing a premeasured amount of tobacco flavor substance, is delivered to the smoker. The circuitry also preferably prevents the actuation of any particular heater more than once, to prevent overheating of the tobacco flavor medium thereon and consequent production of undesired compounds yielding off tastes.
In such an article, the heating elements are disposed of along with the spent tobacco flavor medium. This results in increased costs to the smoker, who must buy new heating elements with each refill of tobacco flavor medium. The volume of material disposed of is also greater when the heating elements must be disposed of.
In addition, when the heating elements are not permanently attached to the article, there is sometimes excessive contact resistance where the removable heaters are electrically connected to the source of electrical energy, resulting in increased power consumption.
Also, when the heating elements are disposable, the resistance may vary from heater to heater, resulting in variations in power consumption when in turn lead to variations in temperature. As it is the temperature to which the tobacco flavor generating medium is heated that determines the characteristics of the tobacco flavor substance, those characteristics will also vary.
It would therefore be desirable to be able to provide an electrical smoking article in which the heating elements are reusable, and of which all disposable portions are biodegradable.
It would also be desirable to be able to provide such an article in which electrical contact resistance between the heaters and the source of electrical energy is minimized.
It would further be desirable to be able to provide such an article in which variation from use to use in the temperature of the heating elements is minimized.